The present invention relates to a three-dimensional image display device for displaying three-dimensional images which an observer can observe without special glasses.
Conventionally, a three-dimensional image display device for displaying three-dimensional images has been used in many ways, for example, for game machines which are provided in amusement arcades, three-dimensional monitors, CAD (computer aided design), and medical instruments.
Generally, an observer can attain a three-dimensional view of an object based on displayed object images, if the object images have parallax therebetween which corresponds to a distance between the observer""s eyes (such images are hereinafter referred to as parallax images) and they are made to be seen by the eyes respectively. The following are typical methods for directing the parallax images to the observer""s right and left eyes respectively, which are applied to three-dimensional image display devices for displaying images based on the foregoing principal.
1. Shutter glasses method: Parallax images for the right eye and those for the left eye are alternately displayed by switching, and the observer is made to wear shutter glasses in which states of right and left shutters are switched in synchronization with the switching of the parallax images. Thus, by this shutter glasses method, parallax images are directed to the observer""s right and left eyes by the switching operation of the shutter glasses.
2. Polarizing glasses method: Polarizing plates having light polarization directions crossing one another are provided before an image for the left eye and that for the right eye, respectively, and the observer is made to wear glasses in which, likewise, polarizing plates having light polarization directions crossing one another are provided so as to come before the right and left eyes respectively. By doing so, parallax images are directed to the observer""s right and left eyes respectively.
3. Parallax barrier method, or lenticular lens method: By providing in front of a display element, a parallax barrier with a plurality of apertures (slits), or a lenticular lens composed of cylindrical lenses provided so as to form a plane surface, an image observation space is formed in front of the parallax barrier or the lenticular lens. The observer is made to observe images with his/her eyes positioned in the space. The following description will explain in detail a three-dimensional image display device to which the parallax barrier method or the lenticular lens method of the foregoing item 3 is applied.
FIG. 14 illustrates a cross section of a three-dimensional (3-D) image display device 50 in which a parallax barrier 71 is installed before a liquid crystal display (LCD) element 51.
As shown in FIG. 15, the LCD element 51 has a TFT substrate 52 and a counter substrate 53, which both are made of glass, and liquid crystal 57 is cramped therebetween. On the TFT substrate 52, TFTs (thin film transistors), not shown, as active elements and pixel electrodes 54 are provided in a matrix form. On the other hand, on the counter substrate 53, there are provided a color filter 55 composed of filters of three colors, red (R), green (G), and blue (B) which are formed at the same pitch as that for the TFTS, and transparent electrodes 56 made of, for example, ITO (indium tin oxide). The LCD element 51 of this type is formed as an active-matrix-type color liquid crystal panel.
Between individual filters of the color filter 55, a black matrix 58 for blocking light with respect to the TFTs and separating individual pixels from one another is formed. The black matrix 58 is normally formed by forming a chrome oxide/metal chrome thin film on the counter substrate 53 and etching the thin film to a desired pattern by the photolithography technique. Therefore, accuracy is required in determining positions of the color filter 53 and the black matrix 58.
Further, on the color filter 55, a transparent color filter protection film 59 is provided, which cancels level differences in the color filter 55 to form a flat surface and prevents electrodes from breaking down. Moreover, alignment films 60 and 61 are provided on surfaces of the TFT substrate 52 and the counter substrate 53 on their sides to the liquid crystal 57, respectively, so that their alignment directions cross each other, for example. On outside surfaces of the TFT substrate 52 and the counter substrate 53 (opposite surfaces thereof to the surfaces on the sides to the liquid crystal 57), there are provided linearly polarizing plates 62 and 63 (see FIG. 14), respectively. Further, on an outside surface of the linearly polarizing plate 62, a backlight, not shown, is provided.
As shown in FIG. 14, a plurality of pixel groups 64, each of which is composed of n pixels, are formed in the LCD element 51. Pixels in the pixel group 64 are arranged as follows:
(R1, G2, B3, . . . Rn), (G1, B2, R3, . . . Gn), (B1, R2, G3, . . . Bn), . . .
where (i) pixels in a pair of parentheses belongs to the same one pixel group 64, (ii) R, G, and B respectively represent pixels which are driven by color signals corresponding to the red color, the green color, and the blue color, and (iii) numerals 1 through n indicate correspondence to parallax images 1 through n, respectively. Thus, the pixels for displaying the parallax images are arranged in an order of Rxe2x86x92Gxe2x86x92B.
Incidentally, n parallax images are n images obtained when viewing an object from n different directions. Such a device wherein n parallax images are used is generally called as multi-view device.
On the other hand, the parallax barrier 71 has a plurality of slits serving as apertures 72 and light blocking sections 73, as shown in FIG. 14. The parallax barrier is disposed in front of the LCD element 51 so that the apertures 72 correspond to the pixel groups 64 of the LCD element 51 at 1:1 ratio.
Light going out from each pixel of the LCD element 51 normally outgoes in all directions from the LCD element 51, but with the foregoing arrangement, lights outgoing from pixels belonging to the same pixel group 64 pass through the same aperture 72, going along optical paths shown by arrows in FIG. 14.
Then, as shown in FIG. 16, observation regions E1, E2, . . . En at which images of xe2x80x9c1xe2x80x9d to xe2x80x9cnxe2x80x9d are observed, respectively, are formed in front of the 3-D image display device 50, by dividing a space there. As a result, in the case where the observer""s eye is placed, for example, in the observation region E1, the observer can observe all the images of xe2x80x9c1xe2x80x9d displayed by the LCD element 51. Thus, by placing the eyes in two regions among the observation regions E1, E2, . . . and En, respectively, the observer facing the LCD element 51 with the parallax barrier 71 therebetween selects two among the images of xe2x80x9c1xe2x80x9d to xe2x80x9cn,xe2x80x9d thereby observing 3-D images. In other words, the observer is allowed to observe various 3-D images depending on viewing angles (positions of the eyes).
On the other hand, FIG. 17 shows a cross section of a 3-D image display device 50 wherein a lenticular lens 81 is provided in front of an LCD element 51. The lenticular lens 81 is composed of a plurality of cylindrical lenses 82 arrayed on a substrate 83 so that the pixel groups 64 of the LCD element 51 and the cylindrical lenses 82 correspond to each other at 1:1 ratio. Therefore, when the observer observes display through the lenticular lens 81, images are selectively viewed depending on the direction of viewing, due to the functions of the cylindrical lenses 82.
For example, in the case where the observer is at a imposition in the same direction with respect to the display as the direction (shown by a solid line arrow in FIG. 17) in which light outgoing from a pixel for displaying an image obtained by viewing an object in a direction of xe2x80x9c1xe2x80x9d (such a pixel is hereinafter referred to as pixel 1) goes so as to pass through a principal point of the cylindrical lens 82, the observer consequently views only an image of the pixel 1, which is displayed only in a region shown by broken lines. Thus, by providing the lenticular lens 81 in front of the LCD element 51, the same effect as that when the parallax barrier 71 is used can be achieved.
Incidentally, regarding the parallax barrier method, or the lenticular lens method, it is necessary to set the pitch of the apertures 72 of the parallax barrier 71 or the pitch of the cylindrical lenses 82, with high precision, so that all the pixels can be viewed from one point of view of the observer. To state differently, the pitch is set with high precision so that all the images of, for example, the pixel 1 can be observed from one point in front of the 3-D image display device 50.
Here, let the pixel pitch of the LCD element 51 be P, a method for the 3-D display be the multi-view method, and a distance between the LCD element 51 and either the parallax barrier 71 or the lenticular lens 81 be d, a pitch p of the apertures 72 or the cylindrical lenses 82 when a display surface (a surface of the parallax barrier 71 or the lenticular lens 81) is observed at a distance therefrom is expressed as:
p=Lxc2x7nxc2x7P/(d+L)xe2x80x83xe2x80x83(1)
Thus, the pitch p of the apertures 72 or the cylindrical lenses 82 has to be set with high precision, so as to satisfy the above formula (1). By doing so, the observation regions E1, E2, . . . En at which n parallax images are observed respectively are formed in front of the 3-D image display device 50 as shown in FIG. 16, thereby allowing the observer to see all the pixels.
Incidentally, as shown in FIG. 16, the observation regions E1, E2, . . . En have a substantially rhombus-shape cross section each. This is because light outgoing from each pixel of the LCD element 51, passing through the parallax barrier 71 or the lenticular lens 81, goes radially. Such lights are composited at a distance L from the display surface, thereby forming the observation regions E1, E2, . . . En in a substantially rhombus-shape cross section each.
A position of the parallax barrier 71 or the lenticular lens 81 with respect to the LCD element 51 may be determined in the following manner.
A maximum width of each of the observation regions E1, E2, . . . En is usually set to an average distance between the observer""s eyes, that is, 65 mm. Let the width be E, and relationship expressed by the following formula is satisfied:
P/d=E/Lxe2x80x83xe2x80x83(2)
Therefore, at such a distance d as satisfies the above formula (2), the parallax barrier 71 or the lenticular lens 81 may be positioned.
In the above description, a general case where the number of parallax images is n has been explained. The following description will explain a concrete case where the number of parallax images is 2, that is, n=2.
FIG. 18 shows a cross section of the 3-D image display device 50 wherein the parallax barrier 71 is provided in front of the LCD element 51, and FIG. 19 shows a cross section of the 3-D image display device 50 wherein the lenticular lens 81 is provided in front of the LCD element 51.
As shown in these figures, two pixels displaying an image directed to the right eye (hereinafter referred to as right-eye image) and an image directed to the left eye (hereinafter referred to as left-eye image) respectively correspond to one aperture 72 or one cylindrical lens 82. In other words, a pixel RR and a pixel GL correspond to one aperture 72 or one cylindrical lens 82. So do a pixel BR and a pixel RL, a pixel GR and a pixel BL, and a pixel RR, and GL. The apertures 72 or the cylindrical lenses 82 have a function of directing right-eye images and left-eye images from the LCD element 51 to the observer""s right eye and left eye, respectively. Arrows in the figures indicate luminous rays going toward the observer""s right eye and left eye.
Incidentally, the pixel RR represents a pixel for the red color which is driven in response to a right-eye image signal, while the pixel GL represents a pixel for the green color which is driven in response to a left-eye image signal. Likewise, the pixel BR represents a pixel for the blue color which is driven in response to the right-eye image signal, the pixel RL a pixel for the red color which is driven by the left-eye image signal, the pixel GR a pixel for the green color which is driven in response to the right-eye image signal, and the pixel BL a pixel for the blue color which is driven by the left-eye image signal.
Here, FIG. 20 shows an arrangement of the pixels displaying the right-eye images and the left-eye images in the LCD element 51. The pixels which are respectively driven in response to the red, green, and blue color signals are arranged in an order as shown in the figure.
The pitch of the apertures 72 or the cylindrical lenses 82 is determined based on the formula (1), and as a result, the pitch is set to twice the pixel pitch of the LCD element 51, or slightly smaller than that. By doing so, as shown in FIG. 21, a position (an observation region) at which all the pixels in the LCD element 51 which display the right-eye images and the left-eye images can be observed is formed in front of the parallax barrier 71. Although not shown in the figures, the same applies to the case where the lenticular lens 81 is used.
FIG. 22 stereoscopically illustrates observation regions formed in front of the 3-D image display device 50. Observation regions F1 and F2 are a region where the right-eye images can be observed and a region where the left-eye images can be observed, respectively, the right-eye and left-eye images being separated by the parallax barrier 71 or the lenticular lens 81. Therefore, by placing the right eye in the observation region F1 and the left eye in the observation region F2, the observer can appreciate a 3-D image based on the right-eye and left-eye images observed. Note that such parallax as makes the right-eye and left-eye images to be recognized as a 3-D image when viewed with both the eyes is previously given to the right-eye and left eye images.
Incidentally, as shown in FIG. 22, observation regions F3 and F4 are also formed outside the observation regions F1 and F2. The observation regions F3 and F4 are formed with light which outgoes from pixels next to the pixels of the LCD element 51 corresponding to the aperture 72 or the cylindrical lens 82 and passes through the same aperture 72 or the cylindrical lens 82. Based on this principle, more observation regions are to be formed outside the observation regions F3 and F4 as well, although they are not shown in the figure.
Therefore, in the observation region F3 beside the observation region F1 for the right-eye image, an image which is originally supposed to be observed by the left eye is observed. In the observation region P4 beside the observation region F2 for the left-eye image, an image which is originally supposed to be observed by the right eye is observed.
However, if the observer observes an image with the right eye placed in the observation region F3 and the left eye placed in the observation region F1, or to state differently, the observer observes with the right eye an image to be observed by the left eye and observes with the left eye an image to be observed by the right eye, a image in which the front and the bottom are reversed is observed. Therefore, it is impossible to achieve the three-dimensional effect of causing the observer to feel as if the image approaches him/her. For this reason, it is necessary to place the right eye in the right-eye image observation region and place the left eye in the left-eye image observation region.
Incidentally, to make the 3-D image display device to display fine 3-D images, it is necessary to increase the number n of the parallax images so as to raise the resolution of the display element. However, in the case where, for example, the number n of the parallax images is increased with the total number of the pixels left unchanged, the resolution of a 3-D image recognized by the observer is 1/n in the case of the multi-view method if the number of parallax is n, and hence a 3-D image obtained is rough, making visibility lower. Therefore, to cause the device to display fine 3-D images without impairing the visibility of the 3-D images, it is necessary to increase the number n of the parallax images while reducing the size of each pixel of the display element.
Here, high precision in determining dimensions and processing is already required in manufacturing the TFTs and the color filter 55 (see FIG. 15) in the LCD element 51. Therefore, in the case where the size of each pixel in the display element is reduced aiming at high resolution, further higher precision in determining dimensions and processing is required in manufacturing the TFTs and the color filter 55. Consequently, manufacture of the LCD element 51 itself is difficult, and the yield of the LCD element 51 lowers, thereby further causing the yield of the 3-D display device to lower.
The object of the present invention is to provide such a three-dimensional (3-D) image display device that: when the number of parallax images of a 3-D image is increased so as to obtain a fine 3-D image, the yield of a display element thereof is improved, and further, the yield of the 3-D image display device is improved.
To achieve the foregoing object, a 3-D image display device of the present invention is characterized by comprising (1) a display element for displaying an image, and (2) an optical path controlling member having a plurality of light transmitting sections which transmit light which is in accordance with the image, the optical path controlling member controlling optical paths so that the light having passed through each light transmitting section reaches a right or left eye of an observer, wherein (i) the display element conducts monochromatic display, and (ii) each light transmitting section of the optical path controlling member is equipped with a color filter for selectively transmitting the light outgoing from the display element.
With the foregoing arrangement, an optical path of light outgoing from the display element is controlled by the optical path controlling member so that the light reaches the observer""s right or left eye. Here, a color filter is formed at each light transmitting section, and each color filter transmits only light having information corresponding to the predetermined color. With this, the observer can observe a 3-D color image.
Incidentally, in the case where the display element is formed by using, for example, a liquid crystal display (LCD) element, the yield of the LCD element is expressed as a product of a yield of a substrate on which active elements are provided (hereinafter referred to as first substrate) and a yield of a substrate on which the color filters are provided (hereinafter referred to as second substrate).
In the aforementioned arrangement wherein the display element is an element for performing monochromatic display, there is no need to provide color filters in the display element. This allows the step of providing color filters to be omitted, thereby making the manufacture of the second substrate easier. As a result, the yield of the second substrate is improved, and accordingly, the yield of the display element is also improved. Further, so is the yield of the 3-D image display device.
Furthermore, since no color filter may be provided in the display element, the structure of the second substrate is simplified. This leads to reduction of the cost of the display element, and further, to reduction of the cost of the 3-D image display device composed of this display element and an optical path controlling member.
For a fuller understanding of the nature and advantages of the invention, reference should be made to the ensuing detailed description taken in conjunction with the accompanying drawings.